TWI644725B - Method for treating fluoride-containing activated alumina - Google Patents

Abstract

A method for treating a fluorine-containing activated alumina, comprising the steps of: providing a fluorine-containing activated alumina; and subjecting the fluorine-containing activated alumina to a desorption step by at least one fluorine desorbing agent for 1 to 3 hours, so that The fluorine-containing activated alumina forms a regenerated activated alumina, wherein a volume ratio of the fluorine desorbing agent to the fluorine-containing activated alumina is between 1 and 3, and the fluorine desorbing agent is selected from A group of sodium hydroxide and ferrous sulfate.

Description

Fluorinated activated alumina treatment method

The present invention relates to a method for treating alumina, and more particularly to a method for treating a fluorine-containing activated alumina.

Fluoride at low doses can help prevent dental caries, but high doses of fluoride can cause tooth or bone damage. The US Environmental Protection Agency stipulates that fluoride in drinking water does not exceed 4 mg/L. For the Republic of China, the maximum limit for fluoride salt in drinking water quality standards is 0.8 mg/L, while the discharge water law rules specify a maximum limit of 15 mg/L for fluoride salts.

For general steel mills, fluorine-containing wastewater from steel mills can usually use activated alumina to adsorb fluorine. However, no studies have yet indicated which specific way to regenerate the activated alumina to reuse the activated alumina.

Therefore, it is necessary to provide a treatment method of fluorine-containing activated alumina to solve the problems of the conventional technology.

An object of the present invention is to provide a method for treating a fluorine-containing activated alumina which is subjected to a desorption step using a specific type of fluorine desorbing agent to obtain a regenerated activated alumina, which can reduce the cost of treating the fluorine-containing wastewater.

Another object of the present invention is that a fluorine desorbent (e.g., sodium hydroxide) after use can be applied to metal-containing wastewater, which can serve as an acid-base regulator in the softening step.

To achieve the above object, the present invention provides a method for treating a fluorine-containing activated alumina, comprising the steps of: providing a fluorine-containing activated alumina; and at least The fluorine-containing desorbing agent performs a desorption step of the fluorine-containing activated alumina for 1 to 3 hours to form the fluorine-containing activated alumina to form a regenerated activated alumina, wherein the fluorine desorbing agent and the fluorine-containing active oxidation The volume ratio of aluminum is between 1 and 3, and the fluorine adsorbent is selected from the group consisting of sodium hydroxide and ferrous sulfate.

In an embodiment of the present invention, in the step of providing the fluorine-containing activated alumina, the method further comprises the step of: adsorbing a fluorine component in a wastewater with an activated alumina to form the fluorine-containing activated alumina.

In one embodiment of the invention, the fluorine desorbent is sodium hydroxide.

In an embodiment of the present invention, after performing the desorption step, further comprising the step of: adding sodium hydroxide after the desorption step to a metal-containing wastewater to adjust an acid-base of the metal-containing wastewater The value is between 9 and 11, wherein the metal-containing wastewater comprises at least one metal ion selected from the group consisting of calcium ions, magnesium ions, iron ions, and manganese ions; The metal-containing wastewater after the pH is subjected to a softening step to soften the metal-containing wastewater.

In one embodiment of the invention, the softening step is carried out through a fluidized bed or a reaction cell.

In one embodiment of the invention, the softening step is carried out through the fluidized bed, and the fluidized bed comprises quartz sand having an average particle size between 0.5 and 1 mm.

In an embodiment of the invention, a rising flow rate of the metal-containing wastewater in the fluidized bed after adjusting the pH value is between 50 and 150 meters per hour.

In an embodiment of the invention, the softening step further comprises adding calcium chloride to the fluidized bed or the reaction cell.

In one embodiment of the invention, the concentration of the fluorine desorbent is between 0.5 and 2.0 wt%.

In an embodiment of the present invention, after performing the desorption step, the method further comprises: performing a washing step on the regenerated activated alumina with a liquid water, wherein a volume ratio of the liquid water to the regenerated activated alumina is Between 1 and 3, and the pH of the liquid water adjusted by an acid solution is equal to or less than 7.5.

10‧‧‧ method

11‧‧‧Steps

12‧‧‧ steps

Fig. 1 is a schematic view showing the flow of a method for treating a fluorine-containing activated alumina according to an embodiment of the present invention.

The above and other objects, features and advantages of the present invention will become more <RTIgt;

Referring to FIG. 1, a method for treating fluorine-containing activated alumina according to an embodiment of the present invention mainly comprises the following steps 11 and 12: providing a fluorine-containing activated alumina (step 11); and desorbing at least one fluorine. a desorption step of the fluorine-containing activated alumina for 1 to 3 hours, so that the fluorine-containing activated alumina forms a regenerated activated alumina, wherein the fluorine desorbent and the fluorine-containing activated alumina have a volume The ratio is between 1 and 3, and the fluorine adsorbent is selected from the group consisting of sodium hydroxide and ferrous sulfate (step 12). The invention will be described in detail below with details of the implementation of the above-described steps of the embodiments and the principles thereof.

The method for treating fluorine-containing activated alumina according to an embodiment of the present invention is first carried out in step 11 of providing a fluorine-containing activated alumina. In the step 11, the fluorine-containing activated alumina adsorbs, for example, a fluorine component in a waste water with an activated alumina to form the fluorine-containing activated alumina. In more detail, the granular (1~10mm) activated alumina may be first filled in the adsorption tower, and then the fluorine-containing wastewater whose pH value is adjusted to 8 or less is provided, and the fluorine-containing wastewater may be firstly filtered by sand or After pre-treatment of the filtration device such as fiber filtration, it is passed through the packed column to permeate the adsorption of fluorine by the activated alumina to remove or reduce the fluorine content in the fluorine-containing wastewater. In one embodiment, the concentration of fluoride ions in the wastewater exiting the packed column can be controlled by varying the filtration rate of the wastewater at the packed column. In a specific example, the lower the filtration rate, the lower the concentration of fluoride ions in the wastewater flowing from the packed column.

The method for treating fluorine-containing activated alumina according to an embodiment of the present invention is followed by step 12: desorbing the fluorine-containing activated alumina with at least one fluorine desorbing agent The step is 1 to 3 hours, so that the fluorine-containing activated alumina forms a regenerated activated alumina, wherein a volume ratio of the fluorine desorbing agent to the fluorine-containing activated alumina is between 1 and 3, and the The fluorine adsorbent is selected from the group consisting of sodium hydroxide and ferrous sulfate. In this step 12, the regeneration effect of the excellent activated alumina is mainly produced by a specific material and a specific ratio of the fluorine desorbing agent. Specifically, for example, when the regenerated activated alumina is used as a raw material for the step 11 (that is, the regenerated activated alumina is filled into the adsorption tower to adsorb the fluorine component of the fluorine-containing wastewater to form the fluorine-containing activated alumina again), The fluorine-containing activated alumina is again subjected to the treatment of the step 12 to form regenerated activated alumina, and the regenerated activated alumina formed again has an adsorption capacity substantially similar to that of the original activated alumina (ie, the activated alumina used for the first time). . In one embodiment, the concentration of the fluorine desorbent is between 0.5 and 2.0 wt%.

It is worth mentioning that if the fluorine desorbent is sodium hydroxide, it has another feature. In one embodiment, when the fluorine desorbing agent is sodium hydroxide, the sodium hydroxide after the desorption step can be added to a metal-containing wastewater to adjust a pH value of the metal-containing wastewater. Between 9 and 11, wherein the metal-containing wastewater comprises at least one metal ion selected from the group consisting of calcium ions, magnesium ions, iron ions, and manganese ions; and adjusting the pH value The subsequent metal-containing wastewater is subjected to a softening step to soften the metal-containing wastewater. Specifically, in the case where the metal-containing wastewater contains calcium ions and/or magnesium ions, sodium hydroxide forms calcium carbonate with a trace amount of hydrogen carbonate (HCO ₃ ^- ) and calcium ions (magnesium ions) contained in the water ( Magnesium carbonate) (ie, the chemical reaction formula is: Ca ²⁺ (Mg ²⁺ ) + HCO ₃ ^- + NaOH → Na ⁺ + CaCO ₃ (MgCO ₃ ) + H ₂ O), and the hydration after the desorption step The fluoride ion in sodium can also react with calcium ions to form calcium fluoride (CaF ₂ ), so that the purpose of reducing calcium ions and magnesium ions (to soften the wastewater) and fluoride ions can be removed. On the other hand, in the case where the metal-containing wastewater contains iron ions and/or manganese ions, when the metal-containing wastewater passes through sodium hydroxide, the pH value is increased to 9.0 or more (for example, between 9 and 11), such as Ferrous ions (Fe ²⁺ ) and manganese ions (Mn ²⁺ ) can be rapidly oxidized by oxygen dissolved in water to form Fe(OH) ₃ and MnO ₂ , so that ferrous and manganese ions can be removed or reduced. purpose.

In one embodiment, the softening step is performed through a fluidized bed. And wherein the fluidized bed comprises quartz sand having an average particle size of between 0.5 and 1 mm. In a specific example, the metal-containing wastewater after adjusting the pH value flows from bottom to top through the fluidized bed, for example, an ascending flow rate in the fluidized bed is between 50 and 150 meters/hour. Softening the metal-containing wastewater.

In one embodiment, the softening step can be carried out through a reaction cell. In a specific example, the metal-containing wastewater after adjusting the pH value is disposed in the reaction tank, and the metal-containing wastewater can be uniformly softened by a stirring method or the like. In another embodiment, when fluoride ions are reacted with calcium-containing wastewater to form calcium fluoride, if the concentration of fluoride ions in the discharged wastewater is too high due to insufficient calcium concentration, calcium chloride may be added to the reaction tank. Increase the calcium salt concentration to avoid excessive fluoride ion concentration. It is worth mentioning that calcium chloride can also be added to the above fluidized bed to increase the concentration of calcium salt to avoid excessive fluoride ion concentration.

In an embodiment, after the adsorbing step, the method further comprises: performing a washing step on the regenerated activated alumina with a liquid water, wherein a volume ratio of the liquid water to the regenerated activated alumina is between 1 and Between 3, and adjusting the liquid water by an acid solution, the pH value is equal to or less than 7.5. The cleaning step is mainly to remove the fluorine desorbent in the regenerated activated alumina. In a specific example, the pH value of liquid water (for example, tap water) can be adjusted by sulfuric acid or hydrochloric acid to maintain a pH value of 7.5 or less after 0.5 hours of washing.

Several examples will be exemplified below to demonstrate that the treatment method of the fluorine-containing activated alumina of the present invention can surely re-form the regenerated activated alumina to have substantially the same fluorine as the original activated alumina (i.e., the activated alumina used for the first time). The adsorption capacity of the ingredients.

Example 1

Example 1 is a wastewater produced by a factory which has been tested to have a fluoride ion of about 100 mg/L, a COD of about 2,500 mg/L, and a sulfate ion of about 170 mg/L. Provide 40 mL of wastewater with a pH of 7.0, add 0.4 g of granular activated alumina (average particle size of about 2 to 3 mm) to carry out batch adsorption test in the wastewater, and carry out residual fluorine in the aqueous solution after 24 hours. Salt analysis to calculate active oxidation The adsorption amount of aluminum can obtain the adsorption amount of the original activated alumina to the fluorine salt of about 3.40 mg/g.

Thereafter, the desorption step is carried out using a fluorine desorbing agent of 0 to 2 wt% sodium hydroxide and/or 0 to 2 wt% ferrous sulfate under the regeneration conditions of Table 1 (a total of 10 sets of conditions), wherein the fluorine adsorbent/activity The alumina volume ratio is about 2. The regenerated activated alumina is further washed with tap water. The volume ratio of the tap water/activated alumina is about 2, and the pH value of the tap water is adjusted with sulfuric acid or hydrochloric acid to stably maintain the pH value of 7.5 or less after 0.5 hours. Taking the experimental condition 1 as an example, the fluorine desorbing agent/activated alumina volume ratio = 2, soaking with 0.5% sodium hydroxide for 0.5 hour, evacuating the sodium hydroxide, and then soaking with 0.5% ferrous sulfate for 0.5 hour. Thereafter, the ferrous sulfate is evacuated and washed with tap water, and the volume ratio of the tap water/activated alumina is 2, and the pH value of the tap water is adjusted with sulfuric acid or hydrochloric acid so that the pH can be stably maintained at 7.5 or less after 0.5 hours.

After the regeneration of the activated alumina, the adsorption test of the original activated alumina to the fluoride salt is repeated, that is, 40 mL of wastewater having a pH of 7.0 is provided, and 0.4 g of the regenerated activated alumina is added to the wastewater for batch preparation. In the adsorption test, the residual fluoride salt analysis of the aqueous solution was carried out after 24 hours to calculate the adsorption amount of the activated alumina, as shown in Table 1 above.

It can be seen from Table 1 that the adsorption amount of the activated alumina to the fluorine salt after regeneration is substantially close to the adsorption amount of the original activated alumina to the fluorine salt, and some operating conditions can even increase the adsorption amount. From this, it can be seen that the treatment method of the fluorine-containing activated alumina of the examples of the present invention does have the effect of forming regenerated activated alumina.

Example 2

The wastewater produced by a plant, after testing, has a fluoride ion of about 100 mg/L, a COD of about 2,500 mg/L, and a sulfate ion of about 170 mg/L. Provide 40 mL of wastewater with a pH of 7.0, add 0.4 g of granular activated alumina (average particle size of about 2 to 3 mm) to carry out batch adsorption test in the wastewater, and carry out residual fluorine in the aqueous solution after 24 hours. Salt analysis to calculate the adsorption amount of activated alumina, the adsorption amount of the original activated alumina to the fluoride salt is about 3.40 mg / g.

Next, a desorption step was carried out using 0.5 wt% sodium hydroxide and 0.5 wt% ferrous sulfate, wherein the fluorine desorbent (sum of sodium hydroxide and ferrous sulfate) / activated alumina volume ratio was about 2. After that, the ferrous sulfate is drained and washed with tap water, and the volume ratio of the tap water/activated alumina is 2, and the pH value of the tap water is adjusted with sulfuric acid or hydrochloric acid, so that the pH can be stably maintained at 7.5 or less after 0.5 hours to obtain Regeneration of activated alumina. After the regeneration of the activated alumina, the adsorption test of the original activated alumina to the fluoride salt is repeated, that is, 40 mL of wastewater having a pH of 7.0 is provided, and 0.4 g of regenerated activated alumina is added to the wastewater for batch adsorption test. The residual fluoride salt analysis of the aqueous solution was carried out after 24 hours to calculate the adsorption amount of the activated alumina. The obtained result is the amount of adsorption of the activated alumina to the fluorine salt after the first regeneration. The amount of adsorption of the activated alumina to the fluorine salt obtained by the above-mentioned regeneration and adsorption step is repeated for the activated alumina once regenerated, and the adsorption amount of the activated alumina to the fluoride salt after the second regeneration is referred to. The inventors of the present invention continuously repeated the regeneration process, and analyzed the adsorption capacity of the regenerated activated alumina to the fluoride salt, and the measured adsorption capacities were all between 2.8 and 3.7 mg/g. It can be seen that the treatment method of the fluorine-containing activated alumina of the embodiment of the present invention has at least another advantage that the fluorine-containing activated alumina can be regenerated many times and can substantially not change the adsorption capacity of its original activated alumina.

Example 3

In Example 3, the waste liquid of the sodium hydroxide of Example 2 was collected as a pH adjuster for metal-containing wastewater having calcium/magnesium/iron/manganese. For the composition of metal-containing wastewater with calcium/magnesium/iron/manganese, please refer to Table 2 below, which is a factory wastewater. Thereafter, the metal-containing wastewater is injected into a fluidized bed using quartz sand (having an average particle diameter of between 0.5 and 1.0 mm) as a medium, and the waste liquid of sodium hydroxide produced in Example 2 is used to adjust the fluidized bed. The metal-containing wastewater has a pH between 10 and 11, and the upward flow rate of the metal-containing wastewater in the fluidized bed is about 80 m/h. For the final water quality detection of wastewater outlets, please refer to Table 3 below.

It can be seen from Tables 2 and 3 above that after the softening step, the ratio of calcium ions, magnesium ions, ferrous ions and manganese ions in the metal-containing wastewater can be reduced, and the concentration of fluoride ions in the sodium hydroxide waste liquid can also be obtained. reduce.

In summary, the present invention provides a method for treating fluorine-containing activated alumina, which has the regenerated activated alumina, can reduce the cost of treating fluorine-containing wastewater, can reduce the production of a large amount of sludge, and can remove fluorine in wastewater. Ion to less than 10 Mg/L to meet the standards for wastewater discharge. Further, the sodium hydroxide waste liquid used in the embodiment of the present invention can also be applied to metal-containing wastewater, which can serve as an acid-base regulator in the softening step.

The present invention has been disclosed in its preferred embodiments, and is not intended to limit the invention, and the present invention may be modified and modified without departing from the spirit and scope of the invention. The scope of protection is subject to the definition of the scope of the patent application.

Claims (10)

A method for treating a fluorine-containing activated alumina, comprising the steps of: providing a fluorine-containing activated alumina; and subjecting the fluorine-containing activated alumina to a desorption step by at least one fluorine desorbing agent for 1 to 3 hours, so that The fluorine-containing activated alumina forms a regenerated activated alumina, wherein a volume ratio of the fluorine desorbing agent to the fluorine-containing activated alumina is between 1 and 3, and the fluorine desorbing agent is selected from A group of sodium hydroxide and ferrous sulfate. The method for treating a fluorine-containing activated alumina according to claim 1, wherein in the step of providing the fluorine-containing activated alumina, the method further comprises the step of: adsorbing fluorine in a wastewater with an activated alumina, The fluorine-containing activated alumina is formed. The method for treating a fluorine-containing activated alumina according to claim 1, wherein the fluorine desorbing agent is sodium hydroxide. The method for treating a fluorine-containing activated alumina according to claim 3, after performing the desorption step, further comprising the step of: adding sodium hydroxide after the desorption step to a metal-containing wastewater, The acid-base value of the metal-containing wastewater is adjusted to be between 9 and 11, wherein the metal-containing wastewater comprises at least one metal ion selected from the group consisting of calcium ions, magnesium ions, iron ions, and manganese ions. a group of people; and a softening step of the metal-containing wastewater after adjusting the pH to soften the metal-containing wastewater. The treatment of the fluorine-containing activated alumina as described in claim 4 of the patent application scope The method wherein the softening step is carried out through a fluidized bed or a reaction cell. The method for treating a fluorine-containing activated alumina according to claim 5, wherein the softening step is performed through the fluidized bed, and the fluidized bed comprises an average particle diameter of between 0.5 and 1 mm. Quartz sand. The method for treating a fluorine-containing activated alumina according to claim 6, wherein a rising flow rate of the metal-containing wastewater in the fluidized bed after adjusting the pH value is between 50 and 150 meters/ hour. The method for treating a fluorine-containing activated alumina according to claim 5, wherein the softening step further comprises adding calcium chloride to the fluidized bed or the reaction cell. The method for treating a fluorine-containing activated alumina according to claim 1, wherein a concentration of the fluorine desorbent is from 0.5 to 2.0% by weight. The method for treating a fluorine-containing activated alumina according to claim 1, wherein after the desorbing step, the method further comprises: performing a washing step on the regenerated activated alumina with a liquid water, wherein the liquid water The volume ratio to the regenerated activated alumina is between 1 and 3, and the pH of the liquid water is adjusted to be equal to or less than 7.5 by an acid solution.